I was going to ask about component sales as I bet there has been a rise in self builds. I built my gaming desktop a year ago and it was much cheaper than a comparable 'off the shelf' rig.Ask Overclockers.co.uk, Aria.co.uk, Scan.com, Ebuyer.com, etc. etc. if their component sales have fallen!
I agree with Nero on the comment regarding Currys and PC World sales. Not a lot of people stroll in and guy a gaming PC off of the shelves there - Mainly because they're complete guff.
A lot of console gamers are defecting to the PC side - The PC Gaming forum reflects that fairly well - A lot of them ask where they can buy a pre-built rig, and OcUK is usually the go-to site; but we encourage them to do it themselves!
As for tablets, I have one and it's ok for a bit of light web browsing but I still find my trusty old laptop to be a more comfortable experience.